[PATCH RFC net-next v2 5/5] selftests/net: packetdrill: add tcp_rcv_neg_window.pkt
From: Simon Baatz via B4 Relay <devnull+gmbnomis.gmail.com@kernel.org>
Date: 2026-02-26 00:49:26
Also in:
b4-sent, linux-doc, linux-kselftest, lkml
Subsystem:
kernel selftest framework, networking [general], the rest · Maintainers:
Shuah Khan, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Simon Baatz <redacted> The test ensures we correctly apply the maximum advertised window limit when rcv_nxt advances past rcv_mwnd_seq, so that the "usable window" is properly clamped to zero rather than becoming negative. Signed-off-by: Simon Baatz <redacted> --- .../net/packetdrill/tcp_rcv_neg_window.pkt | 26 ++++++++++++++++++++++ 1 file changed, 26 insertions(+)
diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt
new file mode 100644
index 0000000000000000000000000000000000000000..15a9b4938f16d175ac54f3fd192ed2b59b0a4399
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt@@ -0,0 +1,26 @@ +// SPDX-License-Identifier: GPL-2.0 + +--mss=1000 + +`./defaults.sh` + +// Establish a connection. + +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 + +0 setsockopt(3, SOL_SOCKET, SO_RCVBUF, [20000], 4) = 0 + +0 bind(3, ..., ...) = 0 + +0 listen(3, 1) = 0 + + +0 < S 0:0(0) win 32792 <mss 1000,nop,wscale 7> + +0 > S. 0:0(0) ack 1 win 18980 <mss 1460,nop,wscale 0> + +.1 < . 1:1(0) ack 1 win 257 + + +0 accept(3, ..., ...) = 4 + +// A too big packet is accepted if the receive queue is empty + +0 < P. 1:20001(20000) ack 1 win 257 +// Send a RST immediately so that there is no rcv_wup/rcv_mwnd_seq update yet + +0 < R. 20001:20001(0) ack 1 win 257 + + +.1 %{ assert tcpi_state == TCP_CLOSE, tcpi_state }% +
--
2.53.0